In large part, the difference in the examples you give is not so much gravity, but other issues
Indeed - that's certainly the case. However, the point i was making is that gravity only seems strong to us because it dominates our behaviour. Different entities' behaviours are dominated by other effects.
I don't think your argument:
In all cases, the amount of damage sustained is controlled primarily by the 'square-cube' law - the strength of the body's structural components goes up as the square of the size, but the mass goes up as the cube of the size.
is applicable - the square/cube law is certainly true, but its implication for animals is that their supporting structure size must increase - so a horse is as strong as an insect, but because its fall is dominated by gravity, its impact speed is such that it's a much greater force than it normally experiences.
One of the reasons we feel more noticeably the effects of gravity is our size. We are (in the scheme of things) really rather large, and have an exact balance of electric charge, so we don't conciously "feel" any electromagnetic pull.
Different size animals have their world dominated by different effects. To paraphrase something i read somewhere: if you drop each of these animals from a height of 5m:
an insect flutters to the ground very slowly
a mouse is unharmed
a cat is unharmed - if it lands correctly
a man breaks his legs
a horse splatters
There are other effects dominating other animals - eg. insects that live on the surface of water are so small that gravity is (for them) irrelevant compared to the effects of surface tension.
I think this is a fascinating article. The physics as to why gravity should weaken when extra dimensions are added for the gravitons to traverse certainly seems sound - and also it offers an intriguing insight into where all that dark matter might be. One thing that bothers me though is this: Why isn't emag (or the strong/weak nuclear force) affected? Why can't it "see" those other dimensions?
Also, I wonder what sort of experiment could possibly test whether these extra dimensions are really needed for grand unification - or whether they're an unnecessary complication.
A 30-pin SIMM, like our TM4100GAD8, can only spit out 8 bits of data at a time.
Hmm... this may have been true in the bad old days, but this chip does a lot better - and it's only a minor upgrade. The designers of the TM4100GAD8 clearly got their act together after the all the fuss of their bodged original release.
IBM make some of the worlds fastest computers - everyone knows that and this latest article seems to suggest that they haven't lost their touch. I'm a bit concerned that they may have bitten off more than they can chew with attempting to simulate nuclear reactions.
I don't understand why people bother simulating nuclear reactions. Now, before you think i'm being facetious, let me explain. Nuclear physics is hard (as if you needed me to tell you that). Most of the theories as to how the fundamental interactions work are flawed. For example, the liquid drop type models (on which most current simulations are based) are incredibly simplistic. They don't even take into account the Pauli exclusion principle, instead relying on a fudge factor to ensure that their particles follow the Fermi-Dirac distribution.
Thus, my argument is: you're better off doing the experiment.
Please remind me again what your claim to being an expert was?
I didn't claim that I'm an expert (my field is optics / astronomy) - if you'd read what i wrote you might have seen that the information i was passing on was from one of the original engineers on the project. His name is Yuri Samarkin. He used to work for this guy. He's not there now. I think he rattled too many cages.
Russians are dealing with lauching spacecrafts since early 40's at least (even earilier, but in 40's they had results). So they probably have couple of clues.
Yes, i agree that the Russian scientists are extremely able. The main problem is resourcing. All throughout the USSR, the fallout from its breakup is a disaster for scientific institutes. I have seen first hand huge once-prolific scientific centres destroyed by lack of funds. It's tragic. Have you ever wondered why there are so many Russian academics in the USA?
Russian politicians simply don't care about the safety of their cosmonauts - they still see the USA as the "old enemy". All they want is to see the spacecraft up there - adequate electrical supply or no.
On reading the press release, it seems that the Russians still haven't got a clue about generating the power required for a space station.
From the press release:
The 42,000-pound Zvezda is 43 feet long (13 meters) and has a solar array wingspan of 97.5 feet (30 meters).
Last time I was in Moscow, as part of an international conference (1998), I had some interesting discussions with one of the designers of the solar array. He voiced his concerns to me that the then planned array size of 60 feet was too small by a factor of 2. It seems that they've added some extra capacity, but nowhere near enough.
So, this mission is doomed to fail. They'll run out of power.
The obvious first take would be to graph the independent variable (time) on the X axis, and learning on the Y.
Hmm, yes i'd never really thought about it like that. I think you're meant to think of it like a hill, where the X axis is how much you know, and the change in height is how much energy you must expend to get to that state of enlightenment.
Edric.
Re:Real Challenge is turning CLI graphical :P
on
Who's Afraid Of C++?
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· Score: 2
Imagine connecting a few icons with a wire to pipe stuff between them, then filling in parameters in a popup window for each of the icons.
What, you mean like LabView ? It's a graphical programming language - mainly intended for controlling lab equipment, but surprisingly general purpose.
But 20/20 vision doesn't saturate the resolution of your eye
Ok, i'll confess i'm not 100% sure of the definition of "20/20". However I can say this with complete assuredness:
If your eyesight does not need correction, then with your pupil size at ~= 2mm (optimal) diameter, then the point-spread function of your eye matches the size of your photoreceptors
As i said, nature knows Nyquist; there's no wastage. The only way to beat this is
Get yourself some damn small photoreceptors:)
Open your pupil to a larger size, and hope that you haven't got any aberrations (unlikely)
Is it contact lenses? Goggles? A new version of lasic surgery?
The usual set up for adaptive optics is to
sense the optical aberrations in the system (in this case your eye - usually it's the atmosphere between your telescope and a star), and then
apply the opposite correction to a flexible mirror (or something similar)
Real adaptive optics corrects for time-varying aberrations (like the stuff that makes stars twinkle) - so a contact-lens type approach wouldn't work for that.
As far as i'm aware, the most useful application for adaptive optics in the human eye is this: to allow physicians to see your retina in enough detail to be able to resolve individual rod/cone cells.
If you have 20/20 vision, then there's no point using adaptive optics (except possibly at night - your vision is considerably worse when using the full aperture of your eye). Your vision is fundamentally limited by the spacing of your rods/cones. And nature knows this - the fundamental optical resolution of your eye matches exactly the rod/cone spacing on your retina! Nature knows about the Nyquist frequency.
As mentioned, at night, the situation is different - the blob of light produced on your retina from a single point (the "point spread function", in optics-speak) is considerably larger than a single photo-receptor cell. So, here there is some scope for adaptive optics to be useful.
They state that the meaurements their instruments make are used to configure some sort of lens - a sort of super glasses.
I'd be very surprised if it was a lens and not a mirror. I did my PhD in making mirrors for adaptive optics - I've met the group from Rochester. Almost all adaptive elements (currently) are reflective - although LCD elements (used in phase rather than amplitude mode) could potentially be used in transmission.
But I wonder if in theory they could use the measurements to smooth out all the imperfections, presumably using laser surgery, and permanently give you the super vision.
Yes, they absolutely could. A guy i shared an office with during my PhD was doing exactly these types of measurements (see here ). He measured my eye, and came out with a complete map of the aberrations - i.e. the deviation from the perfect shape. He discovered that my cornea deviates from ideal by less than 0.5 microns - which is pretty good (i'd need about 0.25 dioptre lens to correct this).
Edric.
Virus to set security settings to paranoid?
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Gnutella VBS Worm
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· Score: 1
I don't really know enough about VB to do this, but shouldn't it be possible to write an ILOVEYOU type thing that propagates around the world, setting everyone's security settings to maximum, (and optionally deleting wscript.exe, or whatever it is you need to run that kind of thing) so that no further viruses like this can happen?
For me, I'd have to say being able to click on an identifier, press a keyboard shortcut, and get help on the identifier (what header file to include, etc.) is the biggest reason I use an IDE. I dunno, can you do that with emacs/vi?
You can using the JDE for Java development under emacs. Check it out here By using a combination of that and emacs' TAGS files, and speedbar, you get just about any IDE feature you want, not tied to any particular language, all in the World's Greatest Editor.
I've seen a lot of crap posted here about the potential uses of laser cooling. When i was doing my PhD, there was a group in the next lab doing laser cooling, so i'm almost qualified to offer an informed opinion. So, here's what laser cooling is good for:
It's good for cooling down small numbers of atoms or ions.
It works by giving each atom/ion the right amount of momentum (from a photon) to slow it to a standstill
It's useful for making bose-einstein condensates (something that's notoriously difficult)
It's useful for making very stable frequency standards (low temperature==low doppler shift==very accurate frequency standard)
It's the last of these items that is likely to prove the making of laser cooling. I don't know if it's happened yet, but there was talk of making the fundamental frequency standards (currently caesium atomic clocks) from laser cooled atoms.
I am no expert at this, but maybe the continuous, analog nature of holograms causes a problem here?
Holograms (in general - not too sure about those used for data storage) store information as the Fourier transform of the scene they're recording. This has two consequences:
A point of light is stored as a series of smooth fringes in the hologram
the fringes for a given point of light extend over the whole of the hologram
So, the analog nature of a hologram isn't so much of a problem. Of course, the resolution of the hologram will limit the data storage capacity, as will the size of the hologram. However, if you lose half of your hologram, you don't lose half your data; your data is just twice as blurry (if that makes sense).
The Ikonos satellite data (see here) shows that it orbits at an altitude of 681 kilometers / 423 miles. Why so close? Because the closer to the earth, the higher the resolution of the picture, all things being equal
One thing that must be borne in mind in this situation is the intrinsic optical disturbance introduced by the atmosphere. This usually restricts the angular resolution of anything looking through it to around a second of arc. So, getting 1m resolution on the ground from a height of 681km suggests better resolution than that - this will not be obtained very often in practice.
The effect of the atmosphere also means that increasing the size of your optics doesn't do any good - you need adaptive optics too if you want to increase resolution. However, doing adaptive optics on wide field of view systems is damn near impossible - it's only any use because in astronomy, your field of view is typically quite tiny.
CO2 is far from being the worst of the greenhouse gasses
... By far the nastiest gasses are NO2 and SO2
Actually, by far the nastiest gas as far as insulating the earth is concerned is H20. Cloud cover provides far more insulation than any amount of C02, methane, or whatever.
Of course, the bad thing about water vapour is that the hotter it gets, the more there's evaporation from the world's oceans.
Slashdot Mirror
I don't think your argument:
is applicable - the square/cube law is certainly true, but its implication for animals is that their supporting structure size must increase - so a horse is as strong as an insect, but because its fall is dominated by gravity, its impact speed is such that it's a much greater force than it normally experiences.See here for more.
Different size animals have their world dominated by different effects. To paraphrase something i read somewhere: if you drop each of these animals from a height of 5m:
- an insect flutters to the ground very slowly
- a mouse is unharmed
- a cat is unharmed - if it lands correctly
- a man breaks his legs
- a horse splatters
There are other effects dominating other animals - eg. insects that live on the surface of water are so small that gravity is (for them) irrelevant compared to the effects of surface tension.Also, I wonder what sort of experiment could possibly test whether these extra dimensions are really needed for grand unification - or whether they're an unnecessary complication.
Lives here . Can't believe that noone else has mentioned it.
I don't understand why people bother simulating nuclear reactions. Now, before you think i'm being facetious, let me explain. Nuclear physics is hard (as if you needed me to tell you that). Most of the theories as to how the fundamental interactions work are flawed. For example, the liquid drop type models (on which most current simulations are based) are incredibly simplistic. They don't even take into account the Pauli exclusion principle, instead relying on a fudge factor to ensure that their particles follow the Fermi-Dirac distribution.
Thus, my argument is: you're better off doing the experiment.
I didn't claim that I'm an expert (my field is optics / astronomy) - if you'd read what i wrote you might have seen that the information i was passing on was from one of the original engineers on the project. His name is Yuri Samarkin. He used to work for this guy. He's not there now. I think he rattled too many cages.
Russian politicians simply don't care about the safety of their cosmonauts - they still see the USA as the "old enemy". All they want is to see the spacecraft up there - adequate electrical supply or no.
From the press release:
Last time I was in Moscow, as part of an international conference (1998), I had some interesting discussions with one of the designers of the solar array. He voiced his concerns to me that the then planned array size of 60 feet was too small by a factor of 2. It seems that they've added some extra capacity, but nowhere near enough.So, this mission is doomed to fail. They'll run out of power.
Hmm, yes i'd never really thought about it like that. I think you're meant to think of it like a hill, where the X axis is how much you know, and the change in height is how much energy you must expend to get to that state of enlightenment.
Edric.
What, you mean like LabView ? It's a graphical programming language - mainly intended for controlling lab equipment, but surprisingly general purpose.
Edric.
Ok, i'll confess i'm not 100% sure of the definition of "20/20". However I can say this with complete assuredness:
If your eyesight does not need correction, then with your pupil size at ~= 2mm (optimal) diameter, then the point-spread function of your eye matches the size of your photoreceptors
As i said, nature knows Nyquist; there's no wastage. The only way to beat this is
Edric
The usual set up for adaptive optics is to
- sense the optical aberrations in the system (in this case your eye - usually it's the atmosphere between your telescope and a star), and then
- apply the opposite correction to a flexible mirror (or something similar)
Real adaptive optics corrects for time-varying aberrations (like the stuff that makes stars twinkle) - so a contact-lens type approach wouldn't work for that.As far as i'm aware, the most useful application for adaptive optics in the human eye is this: to allow physicians to see your retina in enough detail to be able to resolve individual rod/cone cells.
If you have 20/20 vision, then there's no point using adaptive optics (except possibly at night - your vision is considerably worse when using the full aperture of your eye). Your vision is fundamentally limited by the spacing of your rods/cones. And nature knows this - the fundamental optical resolution of your eye matches exactly the rod/cone spacing on your retina! Nature knows about the Nyquist frequency.
As mentioned, at night, the situation is different - the blob of light produced on your retina from a single point (the "point spread function", in optics-speak) is considerably larger than a single photo-receptor cell. So, here there is some scope for adaptive optics to be useful.
Edric.
I'd be very surprised if it was a lens and not a mirror. I did my PhD in making mirrors for adaptive optics - I've met the group from Rochester. Almost all adaptive elements (currently) are reflective - although LCD elements (used in phase rather than amplitude mode) could potentially be used in transmission.
But I wonder if in theory they could use the measurements to smooth out all the imperfections, presumably using laser surgery, and permanently give you the super vision.
Yes, they absolutely could. A guy i shared an office with during my PhD was doing exactly these types of measurements (see here ). He measured my eye, and came out with a complete map of the aberrations - i.e. the deviation from the perfect shape. He discovered that my cornea deviates from ideal by less than 0.5 microns - which is pretty good (i'd need about 0.25 dioptre lens to correct this).
Edric.
I don't really know enough about VB to do this, but shouldn't it be possible to write an ILOVEYOU type thing that propagates around the world, setting everyone's security settings to maximum, (and optionally deleting wscript.exe, or whatever it is you need to run that kind of thing) so that no further viruses like this can happen?
You can using the JDE for Java development under emacs. Check it out here By using a combination of that and emacs' TAGS files, and speedbar, you get just about any IDE feature you want, not tied to any particular language, all in the World's Greatest Editor.
I read that as "SimErection game", which would make a much more amusing game, no?
It's the last of these items that is likely to prove the making of laser cooling. I don't know if it's happened yet, but there was talk of making the fundamental frequency standards (currently caesium atomic clocks) from laser cooled atoms.
Apparently, it "crashed" last night, and they'd been up all night trying to unjam the mechanism (the equivalent of rebooting!) Plus ca change.
Holograms (in general - not too sure about those used for data storage) store information as the Fourier transform of the scene they're recording. This has two consequences:
- A point of light is stored as a series of smooth fringes in the hologram
- the fringes for a given point of light extend over the whole of the hologram
So, the analog nature of a hologram isn't so much of a problem. Of course, the resolution of the hologram will limit the data storage capacity, as will the size of the hologram. However, if you lose half of your hologram, you don't lose half your data; your data is just twice as blurry (if that makes sense).Edric.
One thing that must be borne in mind in this situation is the intrinsic optical disturbance introduced by the atmosphere. This usually restricts the angular resolution of anything looking through it to around a second of arc. So, getting 1m resolution on the ground from a height of 681km suggests better resolution than that - this will not be obtained very often in practice.
The effect of the atmosphere also means that increasing the size of your optics doesn't do any good - you need adaptive optics too if you want to increase resolution. However, doing adaptive optics on wide field of view systems is damn near impossible - it's only any use because in astronomy, your field of view is typically quite tiny.
Edric.
Actually, by far the nastiest gas as far as insulating the earth is concerned is H20. Cloud cover provides far more insulation than any amount of C02, methane, or whatever.
Of course, the bad thing about water vapour is that the hotter it gets, the more there's evaporation from the world's oceans.
Edric.